Episode: S3.03 Unconditional Sex
Scene: Jeff’s coworker Wilma tries to seduce him and he’s telling her about his girlfriend.

Wilma: “She really does exist this girlfriend?”
Jeff: “Oh, oh yeah. She exists. She’s very much an existing person. She’s got tons of existence… Well, not too much of existence. I don’t mean she’s huge or anything. She’s somewhere between completely imaginary and a truck; if you can picture that.”